The Witcher Enhanced Edition when I can be bothered to boot into XP solely to play it...
Otherwise playing spacesims: X2: The Threat (linux) and X3: Reunion (win2k)
(Planning on picking up X3: Terran Conflict soon from gogamer (import retail box since there is no NA distributor other than Steam, and the manual is handy for games like these if for nothing else other than the keymappings... although the X manual tend to be a bit more helpful beyond that or at least for X2 and beyond...)